High-Energy-Density Li-S Batteries with Additional Elemental Sulfur Coated on a Thin-Film Separator.

For the development of high-areal-capacity Li-S batteries, sulfur-coated separators were utilized between the cathode and anode. It was found that (1) the additional sulfur on the separator participated at the electrode reaction occurring in the cathode region, contributing to the improvement of the areal capacity of Li-S batteries, and (2) the areal capacity significantly increased with the mass ratio of sulfur on the separator (S _sep ) to sulfur in cathode (S ₊ ). At the high S _sep /S ₊ mass ratio of 5.0, the Li-S cell delivered fourfold higher areal capacity of 4.28 mAh/cm² than that of the control cell, along with excellent capacity retention of 90% after 50 cycles, demonstrating that the new concept for Li-S cells could be highly advantageous in boosting the Li-S battery cell performance. The new approach can be widely applied to increase the areal capacity and volumetric energy density of Li-S batteries.